The present invention relates to a wiring structure of a semiconductor device and, particularly, to technology that can be effectively adapted to the structure of the first wiring layer in a bipolar-type semiconductor device or in a bipolar CMOS device.
Selective tungsten plugging technology, whole surface tungsten-CVD technology, fellow technology by melting aluminum, aluminum bias sputtering technology, and taper (round) machining technology for connection holes, have heretofore been proposed to improve the state of filling in connection holes such as contact holes or like holes formed in the insulating film, i.e., to improve deposition property of electrically conducting films in a process for forming a first wiring layer of a semiconductor device.
Furthermore, a laminated film structure of a titanium nitride film and an aluminum alloy or like structures have been known to improve reliability of a wiring material such as resistance against migration and like properties in a process of forming a first wiring layer of a bipolar semiconductor device and a bipolar CMOS device.
A semiconductor device having wiring of such a laminated film structure has been described in, for example, U.S. Pat. No. 4,107,726 (Schilling: date of patent, Aug. 15, 1978).
As the bipolar semiconductor devices and bipolar CMOS devices are fabricated in ever fine structures, however, limitation is obviously imposed on the prior art that are related to the bipolar semiconductor devices and bipolar CMOS devices.
In the prior art, the state of filling in connection holes and the reliability of the wiring material can be easily improved by using the laminated film structure of a titanium nitride film and an aluminum alloy together with a hole tapering technique. However, hole tapering becomes difficult as the structure becomes fine. Therefore, another method must be studied in an attempt to improve the state of filling in the connection holes and to improve reliability of the wiring material.
However, the above-mentioned conventional selective tungsten plugging technology which must include peripheral technology such as selecting the tungsten film and adjusting the filling amount, has not yet been established as a mass-production technology. Moreover, tungsten (W) has a large resistance which creates a large CR time constant and develops a signal delay. Therefore, tungsten has heretofore been used for the LSIs of relatively slow speeds but has not been used for such bipolar semiconductor devices as high-speed LSIs or for the bipolar CMOS semiconductor devices. Furthermore, no striking progress can be expected from the fellow technology by melting aluminum or from the aluminum bias sputtering technology in regard to filling the connection holes and improving reliability of the wiring material.